In OFDM based communications systems operating in mobile outdoor radio environments it is advantageous to use decoder outcomes to assist with estimating a communications channel Decoder outcomes are outcomes from a decoder including estimates of the underlying information bit stream and, in some cases, estimates of the output from the corresponding encoder. The estimated channel can then be used to demodulate the received signal, even if the channel is changing during receipt of a data packet.
A data packet typically includes a known initial segment, called a preamble, that allows an initial channel estimate to be formed. A channel estimator uses this preamble-based channel estimate to decode at least the earlier parts of the payload (i.e. the data bearing segment of the data packet following the preamble). Once decoding is performed on the earlier parts of the payload, the channel estimate may be updated based on the decoder outcomes, and may therefore be tracked during receipt of later parts of the payload.
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